1. Field of the Invention
The present invention relates to a method and a device for assisting in controlling, by acting on the collective pitch, the power transmitted to the rotor(s) of helicopters by the engine or engines and the transmission, and/or the rotor speed in autorotation. The invention also relates to heat-propelled helicopters equipped with such a device or using such method.
2. Description of Background and Relevant Information
The driving of the rotors of heat-propelled helicopters requires a drive power that must be precisely controlled, since this power varies or should vary in accordance with various parameters (e.g., pilot demand, flight conditions, temperature, atmospheric pressure, etc.).
Moreover, there are limitations which must not be exceeded, without which the turboshaft engine(s) and/or the transmission could sustain damages which are dangerous to the integrity of the helicopter. These limitations may be grouped into two categories:
mechanical limitations: wherein the maximum torque that the transmission can transmit without sustaining damage (for example, damage to the reduction gear located at the output of the drive shaft of the turboshaft engine);
thermal limitations, which are measured:
either by the maximum generating speed of the gas generator;
or by the maximum temperature of the gasses in the turbine or turbines.
The helicopter pilot must control the power transmitted to the rotor(s) by the turboshaft engine(s) and by the transmission by utilizing the collective pitch in order to ensure that these limitations are not exceeded. To accomplish this, the pilot limits the upward movement of the collective pitch so as not to exceed the mechanical limitations of the transmission and the mechanical or thermal limitations of the turboshaft engine(s) indicated above.
In xe2x80x9cTurbomecaxe2x80x9d engines (Registered Trademark), the first thermal limitation reached is the maximum generating speed of the gas generator, and except in case of damage to the engine, the maximum temperature of the gasses is not reached until after that. Such an engine is said to be Ng-controlled (also known as N1-controlled).
However, most foreign engines generally function in the opposite manner. Such engines are said to be xe2x80x9ct4xe2x80x9d-controlled or xe2x80x9ct45xe2x80x9d-controlled.
In order to observe the status of all of these limitations, the pilot has on the instrument panel several indicators, which can have multiple needles. In all phases of the flight, the pilot must make sure that none of these limits are exceeded. In the take-off and landing phases, in which it is additionally especially necessary to look outside the helicopter, and in which the helicopter often experiences the limits of its capabilities, this is a relatively difficult task which requires the concentration of the pilot.
To make this task easier, retractable stops have been used in certain single-engine aircraft. For example, in xe2x80x9cGazellexe2x80x9d and xe2x80x9cDauphinxe2x80x9d aircraft (Registered Trademarks), these stops are preset by the pilot as a function of the exterior temperature.
Unfortunately, this type of stop can only protect the engine thermally, and only for a given type of flight: e.g., vertical flight is generally chosen for such protection. In essence, the power required by the rotor for a given collective pitch depends on several parameters, i.e., essentially on the atmospheric pressure, the exterior temperature and the travel speed of the helicopter. However, this type of stop does not protect the transmission from the harmful effects of excessive torque, at low altitude, and/or when the transmission is cold.
One object of the present invention is to overcome these drawbacks.
According to the invention, there is provided a method according to which the approach and/or exceeding of a first limitation reached is detected by a computer programmed to actuate a motorized mechanical stop, producing the formation of a hard point countering the continuation of the upward pivoting movement of the collective pitch lever.
According to another characteristic of the invention, this method makes it possible to control the rotor speed of a helicopter in autorotation, and is remarkable in this application in that, upon detection of the approach and/or exceeding of the desired rotor speed by way of a computer programmed for this purpose, the computer is also programmed to activate a motorized mechanical stop preset to a predetermined value of the collective pitch, in order to produce the formation of a hard point or stop constituting an obstacle to the free continuation of the downward pivoting movement of the collective pitch lever.
The invention also provides for a device for assisting the pilot in controlling the power limitations of the turboshaft engine or engines of heat-propelled helicopters. Such a device is remarkable in that it comprises a motorized mechanical stop producing the formation of a hard point or stop countering the continuation of the upward pivoting movement of the collective pitch lever, this motorized mechanical stop being activated by a computer programmed to detect the deviation between the limitations and the corresponding power parameters, to select the greatest one, and to actuate the stop as soon as any of the power limitations are reached or exceeded.
The device for assisting the pilot in controlling the rotor speed of heat-propelled helicopters according to the invention is particularly remarkable in that it comprises a motorized mechanical stop producing the formation of a hard point or stop countering the continuation of the downward pivoting movement of the collective pitch lever, this motorized mechanical stop being activated by a computer programmed to detect the deviation between the limitation of the rotor speed and the current speed, and to actuate the stop as soon as the maximum rotor speed setting given to the computer is reached or exceeded.
According to another characteristic of the invention, the above-mentioned method and device are also remarkable in that the hard point or stop created by the motorization actuated by the computer can be bypassed through the action of a friction coupling placed between the stop or stops and the motorization, in order to allow the pilot to bypass this stop in case of emergency.
According to another characteristic of the invention, the motorized mechanical stop system comprises an electric motor that drives an irreversible reduction gear linked to the collective pitch lever by way of a linkage or transmission, and in that the electromechanical elements of the motorized stop system are placed on an element of the linkage or transmission, this element being constituted in two parts assembled with an ability to move relative to one another, one of these parts being equipped with the stop or stops, while the other carries a stopping device that can be brought into contact with the stop, or with any of the stops, which comprise(s) an electrical system for detecting contact with the stopping device, the stop or stops preferably being adjustable.
From the preceding description, it is clear that the method and the device of the invention can use a system with a single motorized mechanical stop, either to control the power limitations of the turboshaft engine or engines of the helicopter, or to control the rotor speed of the engine.
However, a global solution offered by the invention provides for, in an especially interesting way, creating two mechanical stops motorized by the same motorization mechanism discussed above, and of subjecting them to the first limitation reached in the type of flying that the helicopter is experiencing, and it is this highly advantageous solution that is described in the following description.
Thus, the pilot need only maintain a slight upward pressure on the collective pitch lever to obtain the maximum allowable power. If the pilot releases this pressure and a power limitations is reached, the control system will reduce the collective pitch so that this limitations is not exceeded, but will not accordingly increase the power when it is reduced. It may be said that the pilot is the motoroperator of this control system, which allows him at any time, and without looking at his instruments, i.e., inside, to avoid exceeding the limitations while remaining in the xe2x80x9ccontrol loopxe2x80x9d.
The same device, when the computer receives the rotor speed, can assist in controlling the rotor speed in autorotation. In essence, the lower collective pitch stop must be set so as to provide enough rotor speed in autorotation at its minimum mass, for the low altitude and the minimum temperature at which it is rated. Conversely, when the aircraft is full, if it is flying high and it is hot, and/or if the pilot maintains the pitch at the lower stop, the maximum allowable rotor speed can be easily exceeded. With the method and the device according to the invention, the pilot need only maintain a slight downward pressure on the collective pitch in order to obtain the maximum speed setting that has been given to the computer.
Of course, in any case, a spring or friction device will allow the pilot to bypass this stop in case of emergency.
According to another aspect of the invention, there is provided a method for assisting in controlling at least one power limitation of a helicopter using a computer, at least one motorized mechanical stop, and a collective pitch lever for controlling flight, the method comprising detecting, using the computer, a deviation between the at least one power limitation and at least one corresponding power parameter, selecting, using the computer, a greater one of the at least one power limitation and the at least one power parameter, and actuating, using the computer, the at least one motorized mechanical stop, wherein the at least one motorized mechanical stop is adapted to obstruct the free movement of the collective pitch lever. The at least one motorized mechanical stop may be adapted to counter a free continuation of an upward pivoting movement of the collective pitch lever as soon as the at least one power limitation is reached or exceeded. The at least one power limitation may comprise one of a power limitation of a transmission of the helicopter or a power limitation of at least one turboshaft engine of the helicopter. The method may further comprise bypassing the at least one motorized mechanical stop. The method may further comprise bypassing, in an emergency, the at least one motorized mechanical stop using one of a mechanism and a friction coupling.
The invention also provides for a method for controlling a rotor speed of a helicopter in autorotation, the helicopter including flight controls which comprise a computer, at least one motorized mechanical stop, and a collective pitch lever for controlling flight, the method comprising detecting, using the computer, a deviation between a rotor speed limitation and a current speed, and actuating, using the computer, the at least one motorized mechanical stop, wherein the at least one motorized mechanical stop is adapted to obstruct the free movement of the collective pitch lever. The method may further comprise inputting into the computer a maximum rotor speed setting, wherein the at least one motorized mechanical stop is adapted to counter a free continuation of a downward pivoting movement of the collective pitch lever as soon as the maximum rotor speed setting is reached or exceeded. The method may farther comprise bypassing the at least one motorized mechanical stop. The method may further comprise bypassing, in an emergency, the at least one motorized mechanical stop using one of a mechanism and a friction coupling.
The invention also contemplates a device for assisting in controlling at least one power limitation of at least one turboshaft engine of a helicopter, the device comprising a computer, a collective pitch lever, and at least one motorized mechanical stop controlled by the computer, wherein the at least one motorized mechanical stop is adapted to obstruct the free movement of the collective pitch lever. The at least one motorized mechanical stop may be adapted to counter a free continuation of an upward pivoting movement of the collective pitch lever. The computer may be programmed to detect a deviation between the at least one power limitation and at least one corresponding power parameter. The computer may be adapted to select a greater one of the at least one power limitation and the at least one power parameter. The computer may be adapted to actuate the at least one motorized mechanical stop as soon as the at least one power limitation is reached or exceeded. The device may further comprise a mechanism for bypassing the at least one motorized mechanical stop. The device may further comprise a friction coupling for bypassing, in an emergency, the at least one motorized mechanical stop. The at least one motorized mechanical stop may be part of a motorized mechanical stop system which includes an electric motor, an irreversible reduction gear, at least two electromechanical elements, and a movable element which is adapted to contact each of the at least two electromechanical elements. The motorized mechanical stop system may further include a first shaft coupling the reduction gear to the movable element and a second shaft coupling the movable element to a collective pitch linkage. The motorized mechanical stop system may further include a plate upon which is mounted the at least two electromechanical elements, and wherein the movable element is mounted to the second shaft. The motorized mechanical stop system may further include a plate upon which is mounted the at least two electromechanical elements. The motorized mechanical stop system may further include an electrical system for detecting contact between the at least two electromechanical elements and the movable element. A position of the at least two electromechanical elements may be adjustable. The device may further comprise a friction coupling disposed between the first and second shafts. The device may further comprise a friction coupling disposed between an irreversible reduction gear and at least one of the movable element or the at least two electromechanical elements. The motorized mechanical stop system may further include a safety device disposed between the movable element and a lever which is coupled to a collective pitch linkage, the safety device preventing a mechanical locking.
According to another embodiment, the invention provides for a device for assisting in controlling a rotor speed of a helicopter in autorotation, the device comprising a computer, a collective pitch lever, and at least one motorized mechanical stop controlled by the computer, wherein the at least one motorized mechanical stop is adapted to obstruct the free movement of the collective pitch lever. The at least one motorized mechanical stop may be adapted to counter a free continuation of a downward pivoting movement of the collective pitch lever. The computer may be programmed to detect a deviation between a rotor speed limitation and a current speed. The computer may be programmed with a maximum rotor speed setting and wherein the computer is adapted to actuate the at least one motorized mechanical stop as soon as the maximum rotor speed setting is reached. The device may further comprise a mechanism for bypassing the at least one motorized mechanical stop. The device may further comprise a friction coupling for bypassing, in an emergency, the at least one motorized mechanical stop. The at least one motorized mechanical stop may be part of a motorized mechanical stop system which includes an electric motor, an irreversible reduction gear, at least two electromechanical elements, and a movable element which is adapted to contact each of the at least two electromechanical elements. The motorized mechanical stop system may further include a first shaft coupling the reduction gear to the movable element and a second shaft coupling the movable element to a collective pitch linkage. The motorized mechanical stop system may further include a plate upon which is mounted the at least two electromechanical elements, and wherein the movable element is mounted to the second shaft. The motorized mechanical stop system may further include a plate upon which is mounted the at least two electromechanical elements. The motorized mechanical stop system may further include an electrical system for detecting contact between the at least two electromechanical elements and the movable element. A position of the at least two electromechanical elements may be adjustable. The device may further comprise a friction coupling disposed between the first and second shafts. The device may further comprise a friction coupling disposed between an irreversible reduction gear and at least one of the movable element or the at least two electromechanical elements. The motorized mechanical stop system may further include a safety device disposed between the movable element and a lever which is coupled to a collective pitch linkage, the safety device preventing a mechanical locking.
The invention further provides for a heat-propelled helicopter having a system for assisting in controlling at least one power limitation of a helicopter using a computer, a motorized mechanical stop system having at least one motorized mechanical stop, and a collective pitch lever for controlling flight, the system being adapted to detect, using the computer, a deviation between the at least one power limitation and at least one corresponding power parameter, to select, using the computer, a greater one of the at least one power limitation and the at least one power parameter, and to actuate, using the computer, at least one motorized mechanical stop, wherein the at least one motorized mechanical stop is adapted to obstruct the free movement of the collective pitch lever.
Additionally, the invention provides for a heat-propelled helicopter having a system for controlling a rotor speed of a helicopter in autorotation, the helicopter including flight controls which comprise a computer, a motorized mechanical stop system having at least one motorized mechanical stop, and a collective pitch lever for controlling flight, the system being adapted to detect, using the computer, a deviation between a rotor speed limitation and a current speed, and to actuate, using the computer, the at least one motorized mechanical stop, wherein the at least one motorized mechanical stop is adapted to obstruct the free movement of the collective pitch lever.
A heat-propelled helicopter is also provided which has a system for assisting in controlling at least one power limitation of at least one turboshaft engine of a helicopter, the system comprising a computer, a collective pitch lever, and a motorized mechanical stop system having at least one motorized mechanical stop controlled by the computer, wherein the at least one motorized mechanical stop is adapted to obstruct the free movement of the collective pitch lever.
The invention still further provides for a heat-propelled helicopter having a system for assisting in controlling a rotor speed of a helicopter in autorotation, the system comprising a computer, a collective pitch lever, and a motorized mechanical stop system having at least one motorized mechanical stop controlled by the computer, wherein the at least one motorized mechanical stop is adapted to obstruct the free movement of the collective pitch lever.